This disclosure relates to a system and method for determining load transmitted to a downhole tool in oil and gas recovery operations.
Many downhole tools are subjected to loads during oil and gas recovery operations. For example, packers are used to seal against the flow of fluid to isolate one or more sections, or formations, of a wellbore and to assist in displacing various fluids into the formation and/or retrieving hydrocarbons from the formation. The packers are suspended in the wellbore, or in a casing in the wellbore, from a work string, or the like, consisting of a plurality of connected tubulars or coiled tubing. Each packer includes one or more elastomer elements, also known as packer elements, which are activated, or set, so that they are forced against the inner surface of the wellbore, or casing, and compressed to seal against the flow of fluid and therefore to isolate certain zones in the well. Also, mechanical slips are located above and/or below the packer elements and, when activated, are adapted to extend outwardly to engage, or grip, the casing or wellbore.
The packer is usually set at the desired depth in the wellbore by picking up on the work string at the surface, rotating the work string, and then lowering the work string until an indicator at the surface indicates that some of the slips, usually the ones located below the packer elements, have extended outwardly to engage the casing or wellbore. As additional work string weight is set down on the engaged slips, the packer elements expand and seal off against the casing or wellbore. Alternately, the packer can be set by establishing a hydraulic pressure into a setting mechanism by the work string. The setting mechanism then extends, sets the packer, and expands all slips to engage the casing or wellbore.
Usually, the setting and sealing is accomplished due to the fact that the packer elements are kept sealed against the casing or wellbore by the weight, or load, of the work string acting against the slips. It can be appreciated that it would be advantageous to be able to monitor, evaluate, and, if necessary, vary, the load transmitted to the packer and other downhole packers. Although a weight indicator has been provided at the surface for this purpose, it is often difficult to determine exactly how much load is being transmitted due, for example, to buckling and corkscrewing of the work string, irregular wellbore diameters, etc.
Therefore, what is needed is a system and method for sensing and monitoring the load transmitted to a downhole packer in the above manner so that the load can be evaluated and, if necessary, adjusted.